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cx16 adpcm example is now able to decode and play stereo music as well as mono.

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This commit is contained in:
Irmen de Jong 2023-10-10 02:24:06 +02:00
parent 68e62e4bd2
commit a37769aafe
5 changed files with 255 additions and 55 deletions
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2
docs/source/todo.rst
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@ -1,7 +1,7 @@
TODO
====
- make the adpcm example able to decode and play stereo music.
- stream-wav example: add stereo adpcm support
- [on branch: shortcircuit] investigate McCarthy evaluation again? this may also reduce code size perhaps for things like if a>4 or a<2 ....
- [on branch: ir-less-branch-opcodes] IR: reduce the number of branch instructions such as BEQ, BEQR, etc (gradually), replace with CMP(I) + status branch instruction

56
examples/cx16/pcmaudio/adpcm.p8
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@ -1,6 +1,6 @@
adpcm {
; IMA ADPCM decoder.
; IMA ADPCM decoder. Supports mono and stereo streams.
; https://wiki.multimedia.cx/index.php/IMA_ADPCM
; https://wiki.multimedia.cx/index.php/Microsoft_IMA_ADPCM
@ -8,10 +8,21 @@ adpcm {
; thus compressing the audio data by a factor of 4.
; The encoding precision is about 13 bits per sample so it's a lossy compression scheme.
;
; HOW TO CREATE IMA-ADPCM ENCODED AUDIO? Use sox or ffmpeg:
; HOW TO CREATE IMA-ADPCM ENCODED AUDIO? Use sox or ffmpeg like so (example):
; $ sox --guard source.mp3 -r 8000 -c 1 -e ima-adpcm out.wav trim 01:27.50 00:09
; $ ffmpeg -i source.mp3 -ss 00:01:27.50 -to 00:01:36.50 -ar 8000 -ac 1 -c:a adpcm_ima_wav -block_size 256 -map_metadata -1 -bitexact out.wav
; Or use a tool such as https://github.com/dbry/adpcm-xq (make sure to set the correct block size)
; And/or use a tool such as https://github.com/dbry/adpcm-xq (make sure to set the correct block size, -b8)
; IMA-ADPCM file data stream format:
; If the IMA data is mono, an individual chunk of data begins with the following preamble:
; bytes 0-1: initial predictor (in little-endian format)
; byte 2: initial index
; byte 3: unknown, usually 0 and is probably reserved
; If the IMA data is stereo, a chunk begins with two preambles, one for the left audio channel and one for the right channel.
; (so we have 8 bytes of preamble).
; The remaining bytes in the chunk are the IMA nibbles. The first 4 bytes, or 8 nibbles,
; belong to the left channel and -if it's stereo- the next 4 bytes belong to the right channel.
ubyte[] t_index = [ -1, -1, -1, -1, 2, 4, 6, 8, -1, -1, -1, -1, 2, 4, 6, 8]
@ -29,17 +40,29 @@ adpcm {
15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794,
32767]
uword @zp predict
uword @zp predict ; decoded 16 bit pcm sample for first channel.
uword @zp predict_2 ; decoded 16 bit pcm sample for second channel.
ubyte @requirezp index
ubyte @requirezp index_2
uword @zp pstep
uword @zp pstep_2
sub init(uword startPredict, ubyte startIndex) {
; initialize first decoding channel.
predict = startPredict
index = startIndex
pstep = t_step[index]
}
sub init_second(uword startPredict_2, ubyte startIndex_2) {
; initialize second decoding channel.
predict_2 = startPredict_2
index_2 = startIndex_2
pstep_2 = t_step[index_2]
}
sub decode_nibble(ubyte nibble) {
; decoder for nibbles for the first channel.
; this is the hotspot of the decoder algorithm!
cx16.r0s = 0 ; difference
if nibble & %0100
@ -62,4 +85,29 @@ adpcm {
index = len(t_step)-1
pstep = t_step[index]
}
sub decode_nibble_second(ubyte nibble_2) {
; decoder for nibbles for the second channel.
; this is the hotspot of the decoder algorithm!
cx16.r0s = 0 ; difference
if nibble_2 & %0100
cx16.r0s += pstep_2
pstep_2 >>= 1
if nibble_2 & %0010
cx16.r0s += pstep_2
pstep_2 >>= 1
if nibble_2 & %0001
cx16.r0s += pstep_2
pstep_2 >>= 1
cx16.r0s += pstep_2
if nibble_2 & %1000
cx16.r0s = -cx16.r0s
predict_2 += cx16.r0s as uword
index_2 += t_index[nibble_2]
if_neg ; was: if index & 128
index_2 = 0
else if index_2 > len(t_step)-1
index_2 = len(t_step)-1
pstep_2 = t_step[index_2]
}
}

231
examples/cx16/pcmaudio/play-adpcm.p8
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@ -8,7 +8,7 @@
;
; Simple IMA ADPCM playback example. (factor 4 lossy compressed pcm audio)
;
; NOTE: this program requires 16 bits MONO audio, and 256 byte encoded block size!
; NOTE: this program requires 16 bits MONO or STEREO audio, and 256 byte encoded block size!
; HOW TO CREATE SUCH IMA-ADPCM ENCODED AUDIO? Use sox or ffmpeg:
; $ sox --guard source.mp3 -r 8000 -c 1 -e ima-adpcm out.wav trim 01:27.50 00:09
; $ ffmpeg -i source.mp3 -ss 00:01:27.50 -to 00:01:36.50 -ar 8000 -ac 1 -c:a adpcm_ima_wav -block_size 256 -map_metadata -1 -bitexact out.wav
@ -40,10 +40,15 @@ main {
txt.print_uw(wavfile.sample_rate)
txt.print(" vera rate = ")
txt.print_uw(vera_rate_hz)
txt.print("\n(b)enchmark or (p)layback? ")
txt.print(" #channels = ")
txt.print_ub(wavfile.nchannels)
txt.print("\n\n(b)enchmark or (p)layback? ")
when cbm.CHRIN() {
'b' -> benchmark()
'b' -> when wavfile.nchannels {
1-> benchmark_mono()
2-> benchmark_stereo()
}
'p' -> playback()
}
}
@ -59,58 +64,168 @@ main {
num_adpcm_blocks = (adpcm_size / 256) as ubyte ; THE ADPCM DATA NEEDS TO BE ENCODED IN 256-byte BLOCKS !
}
sub benchmark() {
sub benchmark_mono() {
nibblesptr = &wavdata.wav_data + wavfile.data_offset
txt.print("\ndecoding all blocks...\n")
cbm.SETTIM(0,0,0)
repeat num_adpcm_blocks {
; If the IMA data is mono, an individual chunk of data begins with the following preamble:
; bytes 0-1: initial predictor (in little-endian format)
; byte 2: initial index
; byte 3: unknown, usually 0 and is probably reserved
; If the IMA data is stereo, a chunk begins with two preambles, one for the left audio channel and one for the right channel.
; (so we have 8 bytes of preamble).
; The remaining bytes in the chunk are the IMA nibbles. The first 4 bytes, or 8 nibbles,
; belong to the left channel and -if it's stereo- the next 4 bytes belong to the right channel.
; The code here assumes mono.
adpcm.init(peekw(nibblesptr), @(nibblesptr+2))
nibblesptr += 4
decode_mono_nibbles()
}
repeat 252 {
ubyte @zp nibble = @(nibblesptr)
adpcm.decode_nibble(nibble & 15) ; first word
adpcm.decode_nibble(nibble>>4) ; second word
nibblesptr++
decoding_report(1 + 252*2)
}
sub decode_mono_nibbles() {
; slightly unrolled
ubyte @zp nibble
repeat 252/2 {
unroll 2 {
nibble = @(nibblesptr)
adpcm.decode_nibble(nibble & 15) ; first word
cx16.VERA_AUDIO_DATA = lsb(adpcm.predict)
cx16.VERA_AUDIO_DATA = msb(adpcm.predict)
adpcm.decode_nibble(nibble>>4) ; second word
cx16.VERA_AUDIO_DATA = lsb(adpcm.predict)
cx16.VERA_AUDIO_DATA = msb(adpcm.predict)
nibblesptr++
}
}
}
uword[8] left
uword[8] right
sub benchmark_stereo() {
nibblesptr = &wavdata.wav_data + wavfile.data_offset
txt.print("\n\ndecoding all blocks...\n")
cbm.SETTIM(0,0,0)
repeat num_adpcm_blocks {
adpcm.init(peekw(nibblesptr), @(nibblesptr+2))
nibblesptr += 4
adpcm.init_second(peekw(nibblesptr), @(nibblesptr+2))
nibblesptr += 4
repeat 248/8 {
decode_stereo_nibbles()
nibblesptr += 8
copy_stereo_to_fifo()
}
}
decoding_report(2 + 248*4)
}
asmsub copy_stereo_to_fifo() clobbers(A, Y) {
%asm {{
; copy to vera PSG fifo buffer
ldy #0
- lda p8_left,y
sta cx16.VERA_AUDIO_DATA
lda p8_left+1,y
sta cx16.VERA_AUDIO_DATA
lda p8_right,y
sta cx16.VERA_AUDIO_DATA
lda p8_right+1,y
sta cx16.VERA_AUDIO_DATA
iny
iny
cpy #16
bne -
}}
}
sub decode_stereo_nibbles() {
; decode 4 left channel nibbles
ubyte @zp nibble = @(nibblesptr)
adpcm.decode_nibble(nibble & 15) ; first word
left[0] = adpcm.predict
adpcm.decode_nibble(nibble>>4) ; second word
left[1] = adpcm.predict
nibble = @(nibblesptr+1)
adpcm.decode_nibble(nibble & 15) ; first word
left[2] = adpcm.predict
adpcm.decode_nibble(nibble>>4) ; second word
left[3] = adpcm.predict
nibble = @(nibblesptr+2)
adpcm.decode_nibble(nibble & 15) ; first word
left[4] = adpcm.predict
adpcm.decode_nibble(nibble>>4) ; second word
left[5] = adpcm.predict
nibble = @(nibblesptr+3)
adpcm.decode_nibble(nibble & 15) ; first word
left[6] = adpcm.predict
adpcm.decode_nibble(nibble>>4) ; second word
left[7] = adpcm.predict
; decode 4 right channel nibbles
nibble = @(nibblesptr+4)
adpcm.decode_nibble_second(nibble & 15) ; first word
right[0] = adpcm.predict_2
adpcm.decode_nibble_second(nibble>>4) ; second word
right[1] = adpcm.predict_2
nibble = @(nibblesptr+5)
adpcm.decode_nibble_second(nibble & 15) ; first word
right[2] = adpcm.predict_2
adpcm.decode_nibble_second(nibble>>4) ; second word
right[3] = adpcm.predict_2
nibble = @(nibblesptr+6)
adpcm.decode_nibble_second(nibble & 15) ; first word
right[4] = adpcm.predict_2
adpcm.decode_nibble_second(nibble>>4) ; second word
right[5] = adpcm.predict_2
nibble = @(nibblesptr+7)
adpcm.decode_nibble_second(nibble & 15) ; first word
right[6] = adpcm.predict_2
adpcm.decode_nibble_second(nibble>>4) ; second word
right[7] = adpcm.predict_2
}
sub decoding_report(float pcm_words_per_block) {
const float REFRESH_RATE = 25.0e6/(525.0*800) ; Vera VGA refresh rate is not precisely 60 hz!
float duration_secs = (cbm.RDTIM16() as float) / REFRESH_RATE
floats.print_f(duration_secs)
txt.print(" seconds (approx)\n")
const float PCM_WORDS_PER_BLOCK = 1 + 252*2
float words_per_second = PCM_WORDS_PER_BLOCK * (num_adpcm_blocks as float) / duration_secs
txt.print_uw(words_per_second as uword)
txt.print(" decoded pcm words/sec\n")
float src_per_second = adpcm_size as float / duration_secs
txt.print_uw(src_per_second as uword)
txt.print(" adpcm data bytes/sec\n")
float words_per_second = pcm_words_per_block * (num_adpcm_blocks as float) / duration_secs
when wavfile.nchannels {
1 -> {
txt.print_uw(words_per_second as uword)
txt.print(" decoded mono pcm words/sec (max hz)\n")
}
2 -> {
txt.print_uw(words_per_second as uword)
txt.print(" decoded pcm words/sec\n")
txt.print_uw(words_per_second/2 as uword)
txt.print(" decoded stereo audio frames/sec (max hz)\n")
}
}
}
sub playback() {
nibblesptr = &wavdata.wav_data + wavfile.data_offset
adpcm_blocks_left = num_adpcm_blocks
cx16.VERA_AUDIO_CTRL = %10101111 ; mono 16 bit
when wavfile.nchannels {
1 -> cx16.VERA_AUDIO_CTRL = %10101111 ; mono 16 bit
2 -> cx16.VERA_AUDIO_CTRL = %10111111 ; stereo 16 bit
}
cx16.VERA_AUDIO_RATE = 0 ; halt playback
repeat 1024 {
cx16.VERA_AUDIO_DATA = 0
}
sys.set_irqd()
cx16.CINV = &irq_handler
when wavfile.nchannels {
1 -> cx16.CINV = &irq_handler_mono
2 -> cx16.CINV = &irq_handler_stereo
}
cx16.VERA_IEN = %00001000 ; enable AFLOW
sys.clear_irqd()
@ -128,25 +243,59 @@ main {
; txt.print("audio off.\n")
}
sub irq_handler() {
sub irq_handler_mono() {
if cx16.VERA_ISR & %00001000 {
; AFLOW irq.
;; cx16.vpoke(1,$fa0c, $a0) ; paint a screen color
;; cx16.vpoke(1,$fa0c, $a0) ; paint a screen color
; refill the fifo buffer with one decoded adpcm block (1010 bytes of pcm data)
adpcm.init(peekw(nibblesptr), @(nibblesptr+2))
cx16.VERA_AUDIO_DATA = lsb(adpcm.predict)
cx16.VERA_AUDIO_DATA = msb(adpcm.predict)
nibblesptr += 4
repeat 252 {
ubyte @zp nibble = @(nibblesptr)
adpcm.decode_nibble(nibble & 15) ; first word
cx16.VERA_AUDIO_DATA = lsb(adpcm.predict)
cx16.VERA_AUDIO_DATA = msb(adpcm.predict)
adpcm.decode_nibble(nibble>>4) ; second word
cx16.VERA_AUDIO_DATA = lsb(adpcm.predict)
cx16.VERA_AUDIO_DATA = msb(adpcm.predict)
nibblesptr++
decode_mono_nibbles()
adpcm_blocks_left--
if adpcm_blocks_left==0 {
; restart adpcm data from the beginning
nibblesptr = &wavdata.wav_data + wavfile.data_offset
adpcm_blocks_left = num_adpcm_blocks
txt.print("end of data, restarting.\n")
}
} else {
; it's not AFLOW, handle other IRQ here.
}
;; cx16.vpoke(1,$fa0c, 0) ; back to other screen color
%asm {{
ply
plx
pla
rti
}}
}
sub irq_handler_stereo() {
if cx16.VERA_ISR & %00001000 {
; AFLOW irq.
;; cx16.vpoke(1,$fa0c, $a0) ; paint a screen color
; refill the fifo buffer with one decoded adpcm block (1010 bytes of pcm data)
; left channel
adpcm.init(peekw(nibblesptr), @(nibblesptr+2))
cx16.VERA_AUDIO_DATA = lsb(adpcm.predict)
cx16.VERA_AUDIO_DATA = msb(adpcm.predict)
nibblesptr += 4
; right channel
adpcm.init_second(peekw(nibblesptr), @(nibblesptr+2))
cx16.VERA_AUDIO_DATA = lsb(adpcm.predict_2)
cx16.VERA_AUDIO_DATA = msb(adpcm.predict_2)
nibblesptr += 4
repeat 31 {
decode_stereo_nibbles()
nibblesptr += 8
copy_stereo_to_fifo()
}
adpcm_blocks_left--
@ -164,10 +313,10 @@ main {
;; cx16.vpoke(1,$fa0c, 0) ; back to other screen color
%asm {{
ply
plx
pla
rti
ply
plx
pla
rti
}}
}

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examples/cx16/pcmaudio/small-adpcm-stereo.wav Normal file
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21
examples/cx16/pcmaudio/stream-wav.p8
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@ -242,15 +242,18 @@ interrupt {
cx16.VERA_AUDIO_DATA = lsb(adpcm.predict)
cx16.VERA_AUDIO_DATA = msb(adpcm.predict)
nibblesptr += 4
repeat 252 {
ubyte @zp nibble = @(nibblesptr)
adpcm.decode_nibble(nibble & 15) ; first word
cx16.VERA_AUDIO_DATA = lsb(adpcm.predict)
cx16.VERA_AUDIO_DATA = msb(adpcm.predict)
adpcm.decode_nibble(nibble>>4) ; second word
cx16.VERA_AUDIO_DATA = lsb(adpcm.predict)
cx16.VERA_AUDIO_DATA = msb(adpcm.predict)
nibblesptr++
ubyte @zp nibble
repeat 252/2 {
unroll 2 {
nibble = @(nibblesptr)
adpcm.decode_nibble(nibble & 15) ; first word
cx16.VERA_AUDIO_DATA = lsb(adpcm.predict)
cx16.VERA_AUDIO_DATA = msb(adpcm.predict)
adpcm.decode_nibble(nibble>>4) ; second word
cx16.VERA_AUDIO_DATA = lsb(adpcm.predict)
cx16.VERA_AUDIO_DATA = msb(adpcm.predict)
nibblesptr++
}
}
}
}